Tuning system



B. TREVOR TUNING SY'STEM May 7, 1935.

Filed Feb. 12, 1952 1 INVENTOR .9 BERTRAM TREVOR BY 7 ATTORNEYY v Patented May 7, 1935 UNITED STATES TUNING SYSTEM II Bertram Trevor, Riverl iead, N. asslgnor to Radio Corporation of America, a. corporation of Delaware Application February 12, 1932, Serial No. 592,533

7 Claims.

This invention relates to radio signalling systems and more in particular to receiving systems having means for rendering the systems operative over a widerange of frequencies.

An object of systems of this type is to provide a receiver set which will be self contained and which will receive signals efli'ciently over aplurality of desired wavelength bands.

In general, the present receiver is of the type which includes interchangeable inductan'ces whereby a change of received frequency to' several signalling channels of pre-deter'rnined width may be obtained merely by plugging in another set of tuning inductances.

Another object of this invention is to provide a radio. receiver of the plug-in inductance type in which the inductances for interconnecting"- the several stages are included separate shielded e In radioreceivers adapted to cove'r'awide band of frequencies which comprise a plurality of stages and a plurality of interstage'ccuplin'g inductances;

each included in a separate shielded comparta ment, the several compartments composing a unit which may be plugged into the receiver in one operation,. extremely good shielding will result. Each inductance, however;- will have considerable capacity coupling. to its box or shielding coils tuning capacity. At resonance the greatest current will flow through this capacity: to the grounded box. In this way the connection be-' tween the receiver ground and the metallic compartment enclosing the several interstage inductances is common to all of the tuned circuits. This-gives rise to the transfer of energy between said circuits. This in turn produces regeneration.

which results in an unstable amplifier. 45 An additional object of this invention is to provide a novel plug-in unitin which each of the interstage inductances is individually shielded and in which additional means is provided to prevent interchange of energy between the in- 5 ductances of the several stages due'tothe fact that the composite sl 'iielding unit is inthe path to ground of all of the inductafices'. v In" accordance with this invention the above 5 efi'i'c'ien't grounding betweenthe" inductance" be compartment. Thiscapacity'becomes part ofthe objects are ac'c'o'n'iplished w providing e'i'rtreinhly or container at points adjacent to the respective inductances'. In a preferred embodiment of'the' present invention this grounding isaccornplished by fixing; to the receiver a; plurality of spring I contacts located at points such that the spring 5' contacts make practically perfect contact with the metallic container for thefinductancesat p 'oints' adjacentthe' several indu'ctances. It will be understood that the contacts may be'positioiied at oth 'r'ccnvenient points without departing from the spirit of the invention. I H I I I I Another method of preventing int'fchafig Of energy between the inductances interconnecting the several stages is to providejsjeparate shields for each coil and an insulating strip on which the separate individual shields for the inductance are, mounted. Each inductance container or edit boxis then grounded to the receiver through a separate ground which maybe a" spring contact as described above; In this arrangement the cir C'uit" from one coil box togrdun'df is not; comihch to the circuit from any other coil box to ground. The" novel features of my invention have been set iforth in the claims appended hereto. I The nature; of the invention and the Operation" thereof will e]; understood' by the fol owing detailed description thereof and therefrom when read in connection with the drawir'i ilthrbughbut which likefreferejnce characters indicate like parts and in which:

. F fl 1 we diagrammatically an inters'tage coupling unit in which the severalcoupling mea s are individually shielded and in which the spring contacts for grounding .the metallic coil box at I points adjacent the several tuning means" to the receiver areshown; I I

Figure- 2 i's a plan view of a' portion' of arec'eivefr' showing thecoritacfSf f the pres'entin f vehtion a'r'idsoc'ket's where thec'oil box is plugged m; II I III I Figure 3 hows the chili box; the" tuning mea s" of the'receiver proper, and the thermionic'fstages couplejdby means of said inductances.

Referring to the" drawing; and inparticular to; Figs. 1 and 3; C1 02 c3 and C4 indicate ganged, Inain tuning condensers with a single control K for tuning the receiver over the entire range. Each condenser has; one armature connected to ground; which in thiscaseisjthefnietallic shieldin'e M's-for; the re eive f The other am mreoi ea'c'h on e s r; is can I acted as shown ,tfo male contacts If, which s show'n' e'ii nd'through open inscribe-1* venient points. position on the receiver the contacts I enter the placed in position on the receiver connection between the several inductances in said unit and the tuned capacities C1, C2 etc. is complete.

A plurality of coupling inductances I are enclosed in a container T, each inductance being enclosed in an individual compartment formed by the shield partition members 3. Each inductance has one terminal grounded as shown at 4 to the metallic member T at 4, as shown and the other terminal connected to a female contact member 6. The contact members 6 are positioned as shown adjacent insulated openings 8 in the shield T. When it is desired to change the range over which the receiver will tune, a unit T, having inductrodes I 6 are positively charged from a source S. G.

Balancing or trimming capacities C are connected in parallel with each of the main tuning condensers C1 C2 etc., in order that they may be guarded to tune in step over their entire tuning range.

I claim; 7 g

1. Means for tuning a radio receiver over a wide frequency range comprising, a separate group of capacitive and inductive circuits, a plurality of individually shielded compartments havtances of a predetermined inductive value, is

plugged into the receiver,-that is, is placed in' such a position on the main condenser unit MS that the contacts I connected to the free ends of j the condensers C1 C2 etc., enter the openings 8 in the shield T of the inductance system, which openings are furnishedwith insulators 9 to make contact with the female contact members 6 connected with the free ends of inductances I, thereby completing the individual tuning circuits G1, I. In order that the capacity from the inductance to the box shielded circuit of each individual inductance I be separated, contacts in the form of.

springs S are fastened by rivets orscrews ID, as shown in Figure 2, to thetop of the receiver shield MS. The springs S'which may be composed of any metal and are preferably composed of bronze may be located in any position, preferably at points adjacent the point 4 (see Figs. 1 and 3) in each of the individual compartments of T when the unit is' in position on MS or at other con- When the unit T is placed in contacts 6 while the springs S bear tightly against I the under surface of the unit T at spaced points therealong. Each of the inductances I and each tuning capacity C1 are enclosed in separate compartments having no other openings except the opening 8 between the compartment in T, formed by the partitions 3, and the opening in the receiver shield MS, formed by the partitions 5. The relative position of .the contact members I and 6 and springs S can be seen more clearly by reference to Figure 2 of the drawing.

The unit T is retained in position on the unit.

MS by spring clamps SC shown in Figure 2.

The tuning unit described above is applicable to any type of receiver known today, including receivers in which the several stages are coupled by transformer inductances. For purposes of illustration the unit has been shown to enclose inductances which may be used to interconnect thermionic relay stages, as shown in Figure 3. In

Figure 3 the thermionic tubes I0, 20, 30 and 40 each have a grid electrode ll, 2|, 3| and 4| con nected as shown to the high potential terminal of capacities ci, C2, C3, C4, respectively and to the high potential terminal of an inductance I. The anodes I2, 22, 32 and 42 of tubes I0, 20, 30 and 49 respectively are supplied by direct current potential by inductances I3, 23 and 33 respectively froma source B-|-. Alternating current potentials appearing on the anodes of the respective tubes are impressed on the grid of the following tube through coupling condensers I4, 24 and 34 respectively. The cathodes l5 of each tube are connected as shown through biasing resistances R shunted by by-pass condensers B? to ground as illustrated. The potential variations appearing in the anode circuit oftube 40 may be applied to any load circuit as indicated. Screening elecing capacitive tuning means, a plug-in coil compartment including a plurality of individually shielded inductances, and means comprising separate contact members on each compartment for completing the circuits between each of the individually shielded compartment inductances and capacities when the plug-in unit is placed in position.

2. In radio receiver apparatus, a plurality of thermionic relays, means for coupling said relays in cascade including inductances, an individual shield for each inductance, said shields forming a unit, a tuning device comprising an individual shielded tuning unit for each of said inductances, contacts connected with each tuning unit, a contact connected with each inductance and extending through the shield for said inductance, said contacts adapted to connect said inductance with said tuning means whensaid inductance units are placed on said tuning means, and means for providing a short electrical path between the individual shields containing the tuning means and the individual shields containing inductances comprising a spring contact member mounted on the shield of the tuning unit and bearing directly on each individual inductance shield.

3. Means for tuning a radio receiver over a broad band of frequencies comprising a plurality of, capacity units, each enclosed in an individually shielded compartment, said compartments comprising an enclosed single unit, a connection between one terminal of each of said capacity units and its shield, a contact member connected to the other terminal of said capacity, each contact member extending through an opening in its container and insulated therefrom, a plurality of inductances mounted in a shielded container, each inductance being individually shielded, there being a set of inductances for each frequency band, a connection between one terminal of each inductance and the shielded wall of its container, a contact memberconnected to the other end of each inductance and located adjacent an opening in said container, said contact members being spaced to plug into complementary contact members in said capacity units, and a spring contact member fastened to said first named enclosed single unit adjacent each inductance unit is plugged in.

4. Means for tuning a radio receiver over a wide frequency range comprising, a plurality of capacitive tuning means, individual shielding means and individual shield contacts for each tuning means, a plug-in coil compartment including a plurality of individually shielded inductances, and means comprising separate contact members on each compartment for completing a circuit between each inductance and one of said capacities when the plug-in unit is placed in position.

5. In radio receiver apparatus, a plurality of thermionic relays,,means for coupling said relays in cascade including means for individually When the shielding said coupling means comprising inductances, said individual shields forming a unit, a tuning device comprising a shielded variable capacity unit for each of said inductances, a contact connected with each capacity unit, a contact connected with each inductance and extending through the shield for said inductance, said contacts adapted to connect one of said inductances with each of said tuning capacities when said inductance units are placed on said tuning means, and means for providing a short electrical path between the individual shields containing the tuning capacities and the individual shields containing said inductances comprising a spring contact member bearing on each inductance shield when the unit is plugged in.

6. In radio receiver apparatus, a plurality of thermionic relays, means for coupling said relays in cascade including inductances, an individual shield for each inductance, said shields forming a unit, a tuning device comprising a shielded tuning unit for each of said inductances,

contacts connected with each tuning unit, a contact connected with each inductance and extending through the shield for said inductance, said contacts adapted to connect said inductance with said tuning means when said inductance units are placed on said tuning means, and means for providing a short electrical path between the shields containing the tuning unit and the individual shields containing said inductances comprising a resilient metallic contact member bearing directly on each inductance shield.

7. In radio receiver apparatus, a plurality of thermionic relays, means for coupling said relays in cascade including inductances, an individual shield for each inductance, said shields forming a unit, a tuning device comprising a shielded tuning unit for each of said inductances, contacts connected with each tuning unit, a contact connected with each inductance and extending through insulated openings in the shield for said inductance; said contacts adapted to connect said inductance with said tuning means when said inductance units are placed on said tuning means, and means for providing a short electrical path between the shields containing the tuning device and each of the individual shields containing the said inductances comprising a spring contact member bearing directly on each inductance shield.

BERTRAM TREVOR. 

